At the Hop

Don't let intruders crash your dance. We'll show you how to test your firewalls and intrusion detection systems with hping.

When it comes to penetration testing and security audits, hping is one of your best friends. Currently in its third iteration, hping has become a preferred way to generate IP packets, usually for the purpose of testing firewall and intrusion detection systems.

Because you can use hping to manipulate all of the fields, flags, and protocol types of the TCP/IP protocol suite, some users call it a packet-crafting application.

By manipulating packets, you can scan systems stealthily, generate traffic floods, and generally create packets to your heart's content. Over the years, hping has become the de facto packet generator.

Generating custom packets is nothing new. Previous tools with whiz-bang and hackerish names, such as targa, synful, papa smurf, and netdude, could help with the task of generating designer packets, but many of these older applications had problems and limitations. For example, some tools could only scan Class C IPv4 networks.

Versions

Hping3 is the latest version of hping, and hping2 is the most significant predecessor application. Several applications depend upon hping2, which has been around quite a bit longer than hping3.

I install both versions, and I recommend that you do the same. I use hping3 as a stand-alone application, but I still have hping2 in case I need it for third-party applications, such as scapy (another packet manipulation tool) and idswakeup (an application for auditing intrusion detection systems). Hping3 comes with a new TCL scripting engine and is, therefore, quite bit more powerful than a simple command-line tool.

The original hping and hping2 applications operate as one-time commands – they don't launch an interactive shell. If you use the command without any arguments, hping3 places you into a session, much like the old nslookup command.

Hping3 lets you create fairly sophisticated scripts that will help you simulate traffic for your firewalls and intrusion detection systems. A less obvious advantage of hping3 is that Salvatore Sanfilippo, the creator of all things hping, rewrote much of the underlying code.

What Does hping Do?

Hping provides a single, universal solution that helps prevent many problems of the previous generation. Hping is designed to:

scan hosts,

assist with penetration testing,

test intrusion detection systems,

and send files between hosts.

In this article, I will explain how to start generating test packets with hping.

Installing hping

Hping3 is available from the project website as a source tarball [1]. If you're using an Ubuntu or Debian system, you can use either Synaptic Package Manager or apt-get for the installation. To install hping, enter the following command:

sudo apt-get install hping3.

You don't need to enable any additional repositories. Red Hat or CentOS packages are also available online [2].

Scanning Hosts

After installing hping, you are ready to get started. Suppose you want to send two TCP packets to a system named james, and you want those packets to hit port 80 on james. To do this, you would issue the command shown (with the accompanying output) in Listing 1.

Related content

Linux has a fantastic selection of firewalls for securing stand-alone computers or whole networks. Although you can use IPTables to set up a firewall, the configuration is often the most difficult step. KMyFirewall offers a powerful, user-friendly, GUI-based approach.